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999			_c26939 _d26939
003			OSt
005			20221006154513.0
008			140128s9999 xx 000 0 und d
082			_a630.28 _bLEK/IN
100			_aLekha Rani C
245			_aIntra and interspecifif hybridization in Dendrobium spp.
260			_aVellayani _bDepartment of Plant Breeding and Genetics, College of Agriculture _c2002
502			_bPhD
520	3		_aAn investigation on "Intra and interspecific hybridization in Dendrobium spp." was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, during 1998-2001 with the objective of developing new hybrids of Dendrobium with novel, commercial cutflower qualities for the export market. Fourteen genotypes of Dendrobium comprising of nine commercial varieties, three semi- commercial varieties and two species were selected as parents after initial evaluation. The parental genotypes differed significantly with respect to all the 21 characters studied. High heritability combined with high GCV and genetic advance were observed for length of inflorescence, length of scape, number of flowers per inflorescence and number of nodes per cane. Significant positive inter-correlation in all pair-wise combinations at genotypic and 'phenotypic levels was observed between seven characters viz., number of leaves per clump, height of cane, leaf area per cane, age at first flowering, cane to flower first, vase life and length of inflorescence. The 14 parental genotypes were crossed in all possible combinations (196) after preliminary studies on floral biology, anthesis and pollination. Six combinations could not be attempted as the flowering seasons of the genotypes concerned did not synchronise. A total of 1696 2 pollinations were done covenng 190 (88 crosses + 88 reciprocals + 14 selfs) combinations. Pollinated flowers/immature capsules from 106 combinations abscised at different stages. Green capsules were harvested from 84 combinations. Capsules from three combinations did not contain seeds and seeds from five combinations did not germinate on inoculation. Protocorms/developing seedlings from seven combinations aborted at various stages of in vitro development. Seedlings from 69 combinations were deflasked and transplanted. Two combinations failed to get acclimatized. Progeny from 67 (62 crosses and five selfs) combinations were established successfully in the green house. The levels of incompatibility reactions were grouped under nine heads ranging from flower abscission before the onset of any visible post pollination change to failure of hybrid seedlings to get acclimatized to the ex vitro green house conditions. A total of 123 combinations attempted succumbed to incompatibility at these different stages. Percentage capsule yield ranged from 8 to 33 in the various hybrid combinations. Percentage filled seeds ranged from 10.79 to 75.93 and percentage seed germination ranged from 8.00 to 70.73. The basal medium MS half strength was the best for early germination and rapid in vitro development as compared to MS quarter strength and MS, KC and VW full strengths. The effects of growth hormones, organic additives, sucrose and charcoal on in vitro seed germination and seedling growth were studied and the best concentrations were identified. Transplanting into the humidity chamber under conditions of high relative humidity (85-95%) and controlled irrigation resulted in 94 per cent survival after four weeks. The best among the potting media tried 3 was broken tiles + charcoal + Soilrite (2:2:1), favouring high survival and well balanced post transplantation seedling growth. The 67 hybrid combinations differed significantly with respect to all the eight vegetative characters studied at 1.5 to 2.0 years after transplanting. A partial diallel established with 18 cross combinations revealed the gca effect of P3 to be beneficial for number of shoots per clump, as it was positive and significant. Non additive gene action was responsible for character expression, as dominance variance was higher than additive variance. Sixteen hybrid combinations flowered, recording significant differences for all the 12 floral characters studied. Economic heterosis, relative heterosis and heterobeItiosis of the hybrid combinations were studied for all vegetative and floral characters recorded. Considerable vegetative vigour, earliness and increase in the size of flowers and inflorescences were registered by the hybrid combinations. From the 16 flowering combinations, about 40 promising hybrids were identified. Based on three important criteria viz., novelty, distinctiveness and uniformity of the floral characters, 25 out of these 40 new hybrids were selected. These hybrids show the potential for development into new, indigenous commerical varieties.
700			_aMercy S T (Guide)
856			_uhttp://krishikosh.egranth.ac.in/handle/1/5810015056
942			_2ddc _cTH